28 



AMERICAN HYDRomS. 



ova, so far as 1 can discover arc then withdrawn into the gonangium, not, says Weismann. by 

 contraction of the. tissue.-, lint l>y a resorption process. After the formation of the first atrocyst 

 a number of long processes are given forth from the dcckenplatte which Weismann says contain 

 nutritive matt-rial, and may serve in the nourishment of the gonophores. The present writer 

 has not seen these in vomig blast ost vies, but is unable to tell whether a fully developed gono- 

 phore is the first one. or one of its many successors in a given gonangiutn, as the ae.rocysl seems 

 to be but a transient structure, and may lie replaced several times during the functional lifetime 

 of the gonangium. 



en 1 



90 



^^^H TYPICAL CiiNAXcilA AND CCINOPHOKKS. 



(Lettering as in preceding figures.) 



Fit;. s. r >. I'll' In IK/II knii-iiiili: Inngiliiilinal Mvlinn of female i;onaiit;iiiiii. ^ho\\ ing n i-ingle large ovum in tin- single gniinplinre. 

 Fig. sr,. ScrtulareUa complexa; longitudinal section of male t; n miiis;imn, sliowint; tin- ^jt<-nn:irirs in (In- tila^Iiistylc, Itirn- hcint; no prnpi'r 

 gonophore. 



Fitr. ST. liuintliKJuni nf >i rhilnnlln lilifnrmif. slmwini; liiriir inassrs of ovn. 



Fit:. xx.Hiiilrii/lminiiitJ'iili-itlii: luiii-itniliiiiil sci'linn nf ni:ilc t,'"linTit;iuin, sbnwin.t; s]icrmiirif!.. >-;i. 



Fit;. X'.i. Siiini- species; nviinii across yums; I'i'iiKil,. K.MI.IIIIHH-.., sli.,\vin,t; ri'liitinn nf |rls. 



Fit;, all. Same, spn-i.-s; longitudinal M-ction, iiK-lmlini; IIIVMT part of j;nimni;iiim, and showint; two ova. 



Duiing the formation of the first gonophore there area large number of ova in the blas- 

 tostyle above the point of origin of the gonophore (fig. 70, "/). When the remains of the latter 

 have been largely resorbed after the formation of the acroeyst another gonangium is formed in 

 the same way as the first and another lot of ova are transferred from the endoderm of the 

 blastostyle to the ectoderm of the. new gonophore. and are finally pushed through the top of 

 the gonanium into the aerocvst. 



After the retraction of the remains of the first gonophore from the acroeyst a number of 

 irregular bands and threads -ire seen passing outward and downward to the gonangial walls. 

 These are called % 'gubernacula" by Weismann (fig. SO, <jnl>), and are supposed by him to serve 



